1. Field of the Invention
The object of the present invention is an improved structure of lightning conductor with ionization field, briefly named "radioactive lightning conductor", that is, a lightning conductor wherein the ionization of air surrounding the tip is favoured by radiations, particularly alpha radiations, emitted by radioactive bodies usually in the form of metal strip segments, placed in proximity of the tip itself.
2. Description of the Prior Art
Lightning conductors of this type are already widely known since several years and they form the object, for example, of Italian Pat. No. 487,637 and the respective patents of addition Italian Pat. Nos. 736,138 and 800,082. This last patent, in particular, points out the importance of using Americium 241 as a radioactive substance, the latter having an emission which is exceptionally stable in time and, above all, almost exclusively limited to alpha radiations.
Alpha radiations actually have the advantage, on one hand, to cause a practically negligible air pollution, and on the other hand, of having a high ionizing effect.
According to the same Italian Pat. No. 800,082, the radioactive substance Americium 241 is held into flat, metal containers, the walls of which do not influence outward alpha emission, preventing on the other hand the abrasive action of atmospheric agents, particularly wind, from carrying along in the air particles of radioactive material.
The aforespecified containers are usually applied on the upper surface of an insulator body, associated to the lightning rod and close to its tip, as described in the same Italian Pat. No. 800,082, or even in the already cited Italian Pat. No. 736,138.
In spite of the fact that, with the aforespecified precautions -- namely, the use of a radioactive substance, such as Americium 241, closed inside metal containers -- the pollution determined by the radioactive emission is exceptionally modest, it has however been made to observe that, in practice, said emission is not eliminated (considering the notably long life of such radioactive substances), whereby, as time passes, a progressive pollution takes place, which may reach even appreciable, and hence dangerous levels.